Method for supplying an internal combustion engine with conditioned combustion gas, device for carrying out said method, method for determining the quantities of pollutants in the exhaust gases of an internal combustion engine, and device for carrying out said method

ABSTRACT

The invention relates to a method for supplying an internal combustion engine with conditioned combustion gas, involving the supply of humidity and/or temperature-conditioned combustion gas. The aim of this method is to largely enable the combustion air to be reliably and constantly conditioned even in dynamic operating conditions. To this end, an essentially constant and fully conditioned quantity of combustion gas is provided at each instant, said quantity corresponding to at least the maximum quantity required by the respective internal combustion engine. The invention also relates to a method for determining the quantities of pollutants in the exhaust gases of an internal combustion engine by diluting the exhaust gases using a diluent gas of a known composition. In order to enable the exhaust gases to be diluted in a precisely defined manner, and thus to precisely determine the quantities of pollutants, simply and reliably, an essentially constant and fully conditioned quantity of humidity and/or temperature-conditioned combustion gas is supplied at each instant, said quantity corresponding to at least the maximum quantity required by the respective internal combustion engine, and the exhaust gases are diluted with the quantity of combustion gas which is not used by the internal combustion engine. The invention also relates to devices for carrying out the two methods cited, each comprising a supply line ( 15 ) to the internal combustion engine ( 1 ), for the humidity and/or temperature-conditioned combustion gas, at least one measuring point ( 30 ) for determining the concentration of pollutants, and a determination device ( 32, 33; 41, 42 ) for the flow of a gas, said determination device comprising a passage ( 15 ) for a diluent gas of a known composition. Said devices are characterised in that the supply line or supply passage ( 15 ) is designed for at least the maximum quantity of combustion gas required by the respective internal combustion engine ( 1 ), and a suction pipe ( 2 ) which can be connected to the internal combustion engine ( 1 ) branches off from said supply line ( 15 ).

[0001] The invention relates to a method for supplying an internalcombustion engine with conditioned gas, particularly air, preferably ontest benches, including the supply of humidity and/ortemperature-conditioned gas to the internal combustion engine, as wellas a device to carry out this method and a method for determining thequantities of pollutants in the exhaust gases of an internal combustionengine, including the determination of the pollutant concentration andthe quantity of the flowing exhaust gas whereby diluting of the exhaustgas takes place by using a diluent gas of known composition, andincluding a device to carry out this additional method.

[0002] The condition of the intake air influences the operating behaviorof an internal combustion engine to a great extent. For example, theengine torque increases in gasoline engines with increasing atmosphericpressure by approximately +0.12% per hectopascal. A temperature increaseof the drawn-in ambient air by 1° C. causes in the same case a loss ofpower of approximately −0.5%, for example. The humidity content of theintake air has only minor direct influence on engine power; however, theconsequences relative to exhaust gas emission is not to be disregarded,particularly nitrogen oxide, which can be the case in gasoline enginesas well as in diesel engines. A higher humidity content of the intakeair makes additionally possible in gasoline engines an earlier ignitiontime up to the point of the knocking limit, which has to be consideredduring tuning operation at the engine test bench.

[0003] Since the development of internal combustion engines placesrequirements that are becoming continuously higher relative to theability to reproduce and the accuracy in test results, and based onexhaust gas regulations becoming more stringent worldwide as well as thehigher power density, it is therefore necessary to eliminate allinfluences as much as possible which effect the test results in thedevelopment of engines. Since the intake air is also part of theseinfluences, it is necessary to condition the same to obtain comparabletest conditions at the test bench.

[0004] Known systems for conditioning of the intake air for internalcombustion engines are available commercially (e.g. “Combustion AirConditioning Unit of the firm AVL-List GmbH, Graz, Austria or FEV AirConof the firm FEV Motortechnik GmbH, Aachen, Germany). However, thesesystems are directly connected to the air supply system of the internalcombustion engine and they must follow in this way the changes of theoperating condition of the internal combustion engine and the resultingchange of airflow rate, and these systems must also follow therebydirectly the changes of the rate of airflow of the internal combustionengine itself.

[0005] The maximum rate of airflow in a gasoline engine is about 40times the minimum rate of airflow. It is therefore understandable thatduring rapid dynamic changes of the rate of airflow in a combustionengine, known systems can follow these changes only to a limited degreeand only a poor control quality of the conditions in the air is obtainedduring the dynamic changes in the rate of airflow. An example for aknown system of this type is described in DE 40 15 818 C2.

[0006] In DE 25 36 047 A1 is described, in contrast, a pure negativepressure simulation while no steps are taken for complete conditioningof the combustion air. Furthermore, there is a box provided in thedisclosed device into which enters the combustion air intended forcombustion in the internal combustion engine together with the exhaustgas of the engine, and wherein they may be combined or influence oneanother whereby conditioning (of the air) is made almost impossibleunder reliable and constant conditions. The risk of mixing of combustionair with exhaust gas is very great, especially in highly dynamicoperating conditions in a device such as the one disclosed in DE 25 36047 A1, based on pressure pulsation, wide-reaching turbulence, thermalgradients etc. In addition, the combustion air is drawn into said boxdepending on the demands of the engine, which does almost never allowthe carrying-out of constant conditioning as well.

[0007] The first object of the invention is to avoid these and otherdisadvantages of the traditional conditioning method and conditioningdevices, and to make possible, to a great extent, reliable and constantconditioning of the combustion air even under dynamic and highly dynamicoperating conditions.

[0008] An additional subject area in the field of engine-testingtechnology is the exhaust gas measuring technology by which there is tobe determined the existing pollutant quantities from the measurablepollutant concentrations in the exhaust gas of the engine. For thiscalculation is necessary the quantity (mass) of the flowing exhaust gasfrom which the exhaust gas sample has been taken. This has to bemeasured either directly or it can be determined with the use of thesubsequent balance of the mass flows: supplied air mass+supplied fuelmass=discharged exhaust gas mass. The supplied fuel mass can thereby bemeasured highly accurate and dynamically. Relative to the term“pollutant quantity”, it is to be noted that the subject matter isalmost exclusively pollutant mass in the standards and guidelines forexhaust gas analysis. Sensors to determine pollutants in a gas flowmeasure in general the pollutant concentration, which means the quantityof pollutants—practically exclusively the pollutant mass (e.g. inmilligrams)—relative to a reference quantity of gas (mass or volumeunder actual or under standard conditions). The measured concentrationat the measuring point has to be multiplied by the corresponding flowquantity (mass flow or volume flow).

[0009] A simple system for the accurate use of the balance equation isestablished when either the flow of the supplied air or, especiallyadvantageously, the flow of the discharged exhaust gas is kept constant.This occurs, for example, in the exhaust gas testing technology with theso-called CVS systems (constant volume sampling), which are standardizedand which are established accurate devices for the determination ofpollutant quantities in the exhaust gas. High dilution factors aregenerally required for the CVS systems. Extremely low pollutantconcentrations are created especially in low-pollution engines as aresult thereof, which can almost not be detected any longer by theanalyzers. An alternative to the CVS system for the determination ofpollutant quantities is now the analysis of the undiluted orcomparatively minor diluted exhaust gas in combination with the directmeasuring of either the incoming flow of air mass or, especiallyadvantageous, the flow of exhaust gas mass. However, this method couldnot be carried out properly up to now since the sensors needed for thispurpose have various inherent faults. Among other things, the highdynamic of engine operation and the strong flow pulsation as well as thepressure pulsations overriding the average flow are detected onlyinsufficiently and the sensors are, in general, not sufficiently suitedfor the hot and corrosive exhaust gases. For the solution of theseproblems were proposed suppression chambers and flow-measuringarrangements for the average flow, which have to be built, however,having very large dimensions, which are very difficult to be used on theengine and which oftentimes falsify the conditioned operating conditionsof the engine.

[0010] It was therefore another object of the invention to provide amethod and a device which make possible a precisely defined dilution ofthe exhaust gas and thus a precise determination of the quantities ofpollutants in a simple and reliable manner. The firstly mentioned objectrelative to the conditioning of the combustion gas is achieved accordingto the invention in that an essentially constant and fully conditionedquantity of combustion gas is provided at each instant whereby saidquantity corresponds to at least the maximum quantity required by therespective internal combustion engine. Through this measure,conditioning does not have to be performed again dynamically, but theengine on the test bench has branches (in the supply line) for themaximal required quantity of combustion air diverting the quantity ofcombustion air needed for the actual operating conditions, respectively.The conditioning system disposed upstream (from the engine) has to bedesigned nevertheless for the maximum quantity of combustion air wherebya constant flow of mass passes through the conditioning path in the caseof the invention and whereby control is made correspondingly simple.

[0011] According to an advantageous additional characteristic of theinvention, it is proposed that the combustion gas not used by theinternal combustion engine bypasses the internal combustion engine andis then mixed with its exhaust gas. It is made possible thereby in asimple manner to obtain a small and a roughly adjustable pressuredifferential in the system between the branching-off point of thecombustion air actually needed by the engine and the discharge port ofthe exhaust gas, and thereby is also ensured a substance separation ofcombustion air and exhaust gas.

[0012] A simply realizable negative pressure control of the system canbe achieved if the combustion air/exhaust gas mixture downstream fromthe engine is suctioned out, preferably with a defined negative pressurerelative to the atmospheric pressure.

[0013] Otherwise, there can be proposed alternatively or additionallythat the combustion gas is delivered to the internal combustion engineunder increased pressure relative to the atmospheric pressure—orunneeded combustion gas is diverted to bypass the internal combustionengine.

[0014] It is advantageously proposed thereby that between theconditioned combustion gas and the exhaust gas or the combustiongas/exhaust gas mixture there is set a pressure drop, downstream fromthe internal combustion engine, between 0.3 and 5 mbar, preferablybetween 0.5 and 3 mbar.

[0015] It is made possible thereby to condition (the gas) to pressuresbetween at least—300 mbar and +300 mbar on the intake-side as well as onthe exhaust-side of the engine. This is achieved through a type of CVSmethod with at least a small excess of combustion gas of at leastapproximately 1.2 times the maximum quantity needed by the engine. Thesmall drop in pressure also ensures that the intake as well as theexhaust of the internal combustion engine, or systems disposed upstreamor downstream, are kept essentially on equal pressure level for correctnegative or positive pressure simulation. The actual value measurementfor pressure control occurs preferably at the intake section of theengine, which means that the pressure at the port of the engine exhaustsystem follows the pressure at the intake section within the predefineddrop in pressure.

[0016] According to an additional advantageous characteristic of theinvention, it is proposed that the flow is kept essentially constant,independent from the absolute pressure. With “flow”, it could mean hereand in the following text, a flow of mass as well as a flow of volume asa flowing quantity. At constant flow, there are possible large andpossibly dynamic pressure fluctuations by keeping the small controleffort for the conditioning of gas and the correspondingly simple designof the system is thereby made possible. Diverse known devices may beemployed to keep the flow of combustion gas (air) constant or of othergases developing subsequently, such as (diluted) exhaust gas. Rootsblowers or similar gas moving devices can be employed which move aconstant gas volume per working stroke or rotation so that the flowingmass is dependent on the pressure and temperature of the gas, theworking stroke frequency, or the speed of rotation. Critical nozzle(s)or Venturi tube(s) among others, can be provided having a gas movingdevice (suction fan) downstream in which the quantity of flowing gas isdetermined by the size of the cross section of the respective mostnarrow section in the nozzle(s) and the therein resulting sonicvelocity. This means, that the flowing volume and the flowing mass areonly dependent on the pressure and temperature of the gas upstream fromthe nozzle—but not on the pressure downstream from the nozzle. Anadditional embodiment of a device to keep the flow constant would beuncritical nozzles in which the dependency on backpressure is consideredthrough a respective measuring and control technology. All such devicesto keep the flow constant must be calibrated in the rule. The flow ofinterest (e.g. flow of mass or flow of volume under actual or understandard conditions) is then determined by the corresponding calibrationfactor of the device and by the pressure and temperature of the gas(air) upstream from the device.

[0017] In order to improve high-altitude simulation even more, it isproposed according to an additional characteristic of the invention thatthe direct ambiance of the internal combustion engine is kept at thesame pressure as the pressure of the conditioned combustion gas. Thesame condition exists thereby all over in the area of the internalcombustion engine, which makes the simulation substantially moreaccurate on the test bench at the respectively desired sea level.

[0018] The internal combustion engine is advantageously surrounded by aflow of conditioned combustion gas whereby it is made possible to usethe intake air in this way also as realistic ambient air of the motor,particularly relative to temperature. However, attention must be paidthat sufficient air is moved through the bypass line so that no impropertemperatures develop, particularly temperatures that are too high. Forexample, it can be advantageous in case of possibly provided gas-movingdevices or possibly connected exhaust gas measuring equipment, if thediluent gas fed into the exhaust gas is not hotter than 30° C.,preferably not hotter than 25° C. On the other hand, condensation of thecontained water vapor should not occur in the undiluted nor in thediluted exhaust gas. For this reason, one has to pay attention that thetemperature of the diluted exhaust gas is not too low—or that it doesnot drop below 50° C., for example. Depending on the type ofapplication, it could therefore be necessary to separately adjust thetemperature of the gas in the supply line, e.g. by means of anadditional heat exchanger.

[0019] The second object based on the invention is achieved inaccordance with the characteristics essentially mentioned above in thatan essentially constant and fully conditioned quantity of humidityand/or temperature-conditioned combustion gas is supplied to theinternal combustion engine at each instant whose quantity corresponds toat least the maximum quantity required by the respective combustionengine, and whereby the exhaust gas is diluted with the quantity ofcombustion gas that is not used by the internal combustion engine. Thenovel system can thereby be employed advantageously in the exhaust gastesting technology in which it is used for defined diluting of theexhaust gas. The low excess of combustion gas needed for conditioning ofat least approximately 1.2 times the maximum quantity required by theengine is in most cases set too low for CVS systems—even if there isonly a low requirement on precision demanded relative to the precisionfor measuring the pollutant quantities—and said quantity of excesscombustion gas should thereby be greatly increased, in general. Ittherefore proposed to provide excess in-flowing conditioned combustiongas in the range of at least 4 to 10 times the quantity required by theengine to be used for diluting the exhaust gas of the internalcombustion engine.

[0020] The valves for the flowing quantities (mass) are necessary todetermine now the concentration of the pollutant quantity measured inthe exhaust gas that is actually discharged by the internal combustionengine. According to the first embodiment variation of the invention, itis thereby proposed to keep constant the flow of the discharging gas andthe flow of exhaust gas diluted by the quantity of unused combustion gasand to determine the quantity of combustion gas supplied to the internalcombustion engine as well as the quantity of fuel.

[0021] Since the determination of essentially constant values is verysimple, it can thereby be proposed that the flow of discharging exhaustgas, diluted by the unused quantity of combustion gas, is kept constantand is defined.

[0022] Alternative to the above object, it is nevertheless possible todetermine the quantity of pollutants in that the flow of the suppliedcombustion gas is kept constant, and its quantity and the quantity offuel supplied to the internal combustion engine is determined as well.

[0023] The flow of the supplied combustion gas is thereby keptadvantageously constant and the flow of the diluted exhaust gas isdetermined as well. This variation occurs preferably with a relativelyminor diluted exhaust gas and it has the advantage that requirements forthe flow sensor are considerably lowered since in this case, there is,on one hand, a nearly constant flow of exhaust gas mass and, on theother hand, the exhaust gas pulsates less, is not hot, and is lesscorrosive as a result of the diluted (thinned) air.

[0024] According to an additional characteristic of the invention, it isproposed that the determination of pollutant concentration occurs in theexhaust gas, which is diluted with the quantity of combustion gas notused by the internal combustion engine. Applicable are here also thefacts mentioned above relating to the flow sensor and relating to thesensor or the sampling device for pollutant concentration.

[0025] According to an additional embodiment example of the invention,the determination of the pollutant concentration can, of course, occuralso in the undiluted exhaust gas and the determination is there moredirect and more correct relative to possible other substances carriedalong in the diluent gas.

[0026] If a direct measurement of the pollutant concentration isnecessary, it can be proposed that the pollutant concentration in theavailable combustion gas is determined in addition. This value can beconsidered in the determination of the quantity of pollutants emitted bythe internal combustion engine.

[0027] In the method for the determination of the quantity ofpollutants, is can be advantageously proposed that the quantity ofavailable combustion gas is a multiple of the maximum quantity requiredby the combustion engine.

[0028] The determination of pollutant emission is also necessary atdifferent sea-level conditions and/or environmental conditions so thatthis simulation can be provided here also in that the combustiongas/exhaust gas mixture downstream from the internal combustion engineis moved by suction, preferably by a defined negative pressure relativeto the atmospheric pressure—or that the combustion gas is delivered tothe internal combustion engine through increased pressure relative tothe atmospheric pressure or whereby unneeded combustion gas bypasses theinternal combustion engine.

[0029] In each case it is thereby again of advantage if there is set apressure drop between 0.3 and 5 mbar, preferably between 0.5 and 3 mbar,between the conditioned combustion gas and the exhaust gas or thecombustion gas/exhaust gas mixture downstream from the internalcombustion engine.

[0030] In the determination of pollutants in the exhaust gas, the flowis kept advantageously and essentially constant, independent from theabsolute pressure.

[0031] Precise simulation of various sea-level conditions and/orenvironmental conditions may also be achieved through the method ofexhaust gas testing if the direct ambiance of the internal combustionengine is kept at the same pressure as the pressure of the conditionedcombustion gas, or if a flow of conditioned combustion gas surrounds theinternal combustion engine.

[0032] Attention must be paid thereby, particularly during the use ofnegative pressure for high-altitude simulation, that the respectivemeasuring device is also under the ambient air pressure; however, thesemeasuring devices are generally not designed for an exhaust gas pressureof down to −300 mbar. It is therefore to be proposed that the negativepressure existing during exhaust gas analysis must be compensated withan additional pump. In measuring with the CVS system, double dilution isnot permissible in the LD range. The following possibilities existtherefore in taking measurements: either diluted modal exhaust gastesting (analysis), however, exclusively with heated analyzers based onthe low dilution ratio, additional measuring of the (almost) constantairflow upstream from the branching-off point of the supply line to theinternal combustion engine—or, the entire system is to be enlarged insuch a manner that minimum dilution rates of rdil≧4 are achieved.

[0033] The first object stated in the beginning is also achievedaccording to the present invention through a device to supply aninternal combustion engine with conditioned combustion gas whereby saiddevice comprises a supply line leading to the internal combustion enginefor humidity and/or temperature-conditioned combustion gas, and possiblya blower in the supply line, and said device is characterized in thatthe supply line or supply passage is designed for at least the maximumquantity of combustion gas required by the respective internalcombustion engine whereby a suction pipe, which can be connected to theinternal combustion engine, branches off from said supply line. Besidethe advantages mentioned already above relative to the method, thedescribed inventive device with its supply line has the advantage thatthere exists a good flow characteristic, which ensures for thecombustion air in the engine that no backup-mixing of exhaust gases cantake place and that there is no change in the parameter of theconditioned combustion air.

[0034] According to an additional characteristic of the invention, anexhaust gas line, connectable to the internal combustion engine, joinsthe supply line downstream from the branching-off point of the intakeline. Thereby is offered the possibility of negative pressure controlwhile maintaining all previously mentioned advantages.

[0035] In the inventive device are also advantageously provided elementsfor the adjustment of a pressure differential in the range between 3.5and 5 mbar, preferably between 0.5 and 3 mbar, which are disposedbetween the branching-off point of the intake line and the merging pointof the exhaust gas line with the respective supply line. Thus, areliable substance separation can be guaranteed between combustion airand exhaust gas for all operational conditions of the engine—from idlingup to full power.

[0036] This effect can be obtained in the same way—or it can beadditionally guaranteed—if there are provided devices to ensure aminimum flow rate between the branching-off point of the intake line andthe merging point of the exhaust gas line, at least corresponding to thediffusion rate of exhaust gas in the conditioned combustion gas.

[0037] Apart from the possibility of connecting the inventive device toa central conditioning system, it is also possible to includeconditioning with the inventive device itself whereby, in this case, thedevices for adjustment and control of the temperature and/or humidityare provided upstream from the branching-off point of the intake line inthe supply line leading to the internal combustion engine, e.g. gascoolers, mist eliminators, gas heaters and vapor delivery lines,preferably having vapor metering valves.

[0038] In one embodiment of the inventive device it is proposed that agas-moving device be provided to be able to conduct positive pressurecontrol whereby said gas-moving device is disposed upstream from thebranching-off point of the intake line and a control device is provideddownstream from the merging point of the exhaust gas line for the gasflow.

[0039] Otherwise, negative pressure control is possible if a controldevice for the gas flow is provided upstream from the branching-offpoint of the intake line and a gas-moving device is provided downstreamfrom the merging point of the exhaust gas line. Both of theabove-mentioned control variations can be used in combination, ofcourse.

[0040] At least one heat exchanger is advantageously provided betweenthe internal combustion engine and the gas-moving device to avoiddifficulties in the design of the gas-moving device, particularly in theform of a centrifugal blower of a radial blower, whereby an exhaustgas/air mixture could develop during the operation of the system atgreat negative pressure and/or based on turbulence. Operation undernegative pressure is thereby possible, even up to approximately 500 mbar(which corresponds to approximately 6,000 meters above sea level.)

[0041] Relative to the choice of gas-moving devices, suitable types tobe selected depend on the respective requirements. For example, thereare two advantages in case of Roots blowers: On one hand, negativepressures up to 550 mbar are no problem (this is necessary to ensure−500 mbar in the suction pipe) whereas centrifugal blowers have a limitof approximately 450 mbar in the desired dimensions. On the other hand,the negative pressure as well as the positive pressure can be controlledby means of a speed-controlled Roots blower and thus a butterfly valveis unnecessary at the end of the collecting box since the flow can berestricted by means of the Roots blower. However, a throttle valve isarranged for negative pressure operation after the conditioning path andupstream from the engine so that the conditioning path is not biased bygreat negative pressure.

[0042] The Roots blower moves a nearly constant volume flow at constantspeed, independent from the air pressure. However, the air-mass flowchanges correspondingly to the changes in pressure. The throttle valvecan be correspondingly adjusted depending on the air pressure to keepthe air-mass flow nearly constant in the conditioning path (theseadjustments are determined during operation and are forwarded to thecontrol device accordingly.) Pressure control occurs then through speedcontrol of the Roots blower (for instance, via PID(proportional-integral-differential) control devices.)

[0043] The disadvantage of the Roots blower lies in the maximum possibletemperature of the delivered gas mixture, which is limited toapproximately 50-60° C. Should there only be required negative pressuresof approximately 350 mbar, then one can resort to the centrifugal blowerthat can be operated at a temperature of up to approximately 150° C.

[0044] Control of quantity can be accomplished in a simple and reliablemanner if the control devices for the gas flow are designed in the formof butterfly valves.

[0045] A precision control valve may be provided thereby in anadvantageous manner parallel to the butterfly valves.

[0046] In addition, substance separation can be ensured if a gas-movingdevice is provided between the branching-off point of the intake lineand the merging point of the exhaust line. The desired pressuredifferential between the intake-side and exhaust-side of the engine canbe adjusted or influenced through said gas-moving device.

[0047] According to an additional embodiment or in combination with oneof the above-described devices, substance separation may also beachieved in that devices are provided for the laminarization of the flowin the supply line, preferably at least between the branching-off pointof the intake line and the merging point of the exhaust gas line.

[0048] An additional alternative to achieve this effect is to provide ashock drag and/or a muffler in the supply line between the branching-offpoint of the intake line and the merging point of the exhaust gas line.

[0049] For the simple and economical design of the system, highlydynamic events should have no effects on the internal combustionengine—or it should have only the smallest effects on the requiredquantity of conditioned gas. According to an advantageous embodiment ofthe invention, the device is characterized in that at least one of thegas-moving devices is in controlled communication with the oppositecontrol device, relative to the internal combustion engine, for the gasflow. A control concept can be realized thereby, which keeps the flowthrough the system essentially constant even under dynamic pressurechanges.

[0050] The moving capacity of the gas-moving device is therebyadvantageously adjustable dependent on the position of the controldevice disposed on the opposite side. If, for example, a throttle valveis adjusted to the change of pressure operating in the system—or of apressure sequence—then the speed of a gas-moving device designed as acentrifugal blower, for example, is matched in such a manner that theflow quantity of conditioned gas remains essentially constant,independent from the absolute pressure.

[0051] It is proposed according to an additional characteristic of theinvention, that to make an engine test as real as possible underprecisely defined conditions, the distance between the branching-offpoint of the intake line and the merging point of the exhaust gas lineshould correspond substantially to the distance between the air filterintake and the end of the muffler system of the vehicle whose internalcombustion engine is supplied with conditioned combustion gas.

[0052] According to an additional characteristic of the invention, it isproposed that a closed space is provided to receive the internalcombustion engine whereby said closed space is connected to the sectionof the supply line between the branching-off point of the intake lineand the merging point of the exhaust gas line. The engine to be testedis thereby biased with the pressure existing in the connecting linewhereby said pressure influences the engine from the outside, which is agreat advantage, particularly in high-altitude simulation (low airpressure).

[0053] Advantageously there is provided a closed space to receive theinternal combustion engine in the section between the branching-offpoint of the intake line and the merging point of the exhaust gas line.This space formed by a closeable and sealable box, relative to theambiance, can be a component of the engine test bench and can therebyremain on the test bench if another engine is to be tested on the (same)test bench. However, the box is advantageously a component of the palletonto which the engine is installed and which is made for transportingand stabilizing the engine on the test bench.

[0054] For the achievement of the second object, which is based insubstance on the invention, there is provided a device to determine thequantities of pollutants in the exhaust gas of an internal combustionengine comprising at least one measuring point, for example a sensor orsampling device, for determination of the pollutant concentration, and adetermination device for the flow of gas whereby said determinationdevice is provided with a passage leading from the exhaust gas passageto the supply passage for a diluent gas of known composition. Accordingto the invention, this passage is characterized in that the supplypassage for the diluent gas is designed for at least the maximumquantity of combustion gas required by the respective internalcombustion engine and whereby an intake line (suction pipe), which canbe connected to the internal combustion engine, branches off from saidsupply passage. The determination device to determine the constant ornearly constant flow (mass or volume) of combustion gas (air) or of(diluted) exhaust gas can be realized in various known ways, forinstance with a flow sensor for the mass or volume flow, such as ahot-wire (thermal) or an ultrasound measuring system, or a measuringsystem for pressure and temperature of the gas, disposed directly infront of the device, to keep the flow constant whereby the calibrationconstant and possible other values of this device are considered in thedetermination of the flow (e.g. the speed of the Roots blower.)

[0055] The supply passage for the diluent gas is thereby advantageouslydesigned for a multiple of the maximum quantity of combustion gasrequired by the respective internal combustion engine.

[0056] According to an additional characteristic of the invention, themeasuring point to determine the pollutant concentration in the exhaustgas passage is arranged downstream from the merging point of the exhaustgas passage into the supply passage for the diluent gas, to lower therequirements for the sensor or sampling device and to employ said sensorwhere a nearly constant exhaust-gas mass flow exists, on one hand, andwhere, on the other hand, the exhaust gas pulsates less, is not as hot,and is less corrosive.

[0057] In contrast, a more precise measurement is possible with robustsensors or instruments (since it is conducted in a direct manner) if themeasuring point for the determination of the pollutant concentration inthe exhaust gas passage is arranged upstream from its merging point intothe supply passage of the diluent gas.

[0058] An additional measuring point to determine the pollutantconcentration is advantageously provided in the supply passage for thediluent gas, upstream from the merging point of the exhaust gas passageinto said supply passage, to be able to additionally consider thepollutant burden of the diluent gas.

[0059] The same effects and advantages as mentioned above can beachieved relative to the determination device for the flow of a gas, ifsaid determination device is arranged in the same section as themeasuring point for the determination of the pollutant concentration.

[0060] According to an alternative embodiment of the inventive device,there is a determination device for the flow of gas provided in thesupply passage for the diluent gas and there is also advantageouslyprovided a measuring device for the fuel mass delivered to the internalcombustion engine whereby these devices are provided to carry out amethod to determine the flow of mass of the exhaust gas with the use ofa balance equation of supplied combustion gas and supplied fuelquantity. However, both devices may also be provided as a single unit orin combination for calibration or for checking the values detecteddirectly by sensors.

[0061] The invention is to be described in more detail in the followingdescription with the aid of accompanying drawings.

[0062]FIG. 1 shows thereby schematically a system according to theinvention for positive pressure operation and negative pressureoperation.

[0063]FIG. 2 is an illustration according to FIG. 1 for positivepressure control and negative pressure control without compensation forloss of pressure.

[0064]FIG. 3 is an illustration according to FIG. 1 for positivepressure control only.

[0065]FIG. 4 is an illustration according to FIG. 1 for negativepressure control only.

[0066]FIG. 5 is an illustration according to FIG. 1 for highly precisenegative and positive pressure control.

[0067]FIG. 6 is a schematic illustration of a system according to theinvention with a test piece consisting of an engine provided with anintake section and an exhaust gas section.

[0068]FIG. 7 relates to FIG. 6 whereby the entire engine is disposedinside a closed space.

[0069]FIG. 8 is a version of the system in FIG. 7 with the box as aflow-through part of the supply line.

[0070]FIG. 9 corresponds to FIG. 6 whereby measuring points or samplingpoints are provided for measuring pollutant quantities.

[0071]FIG. 10 is an embodiment of the invention corresponding to FIG. 9,but with another arrangement of the measuring points or sampling pointsand the sensors.

[0072]FIG. 11 is an embodiment according to FIG. 6 with yet anotherarrangement of the measuring points or sampling points and the sensors.

[0073]FIG. 12 illustrates an embodiment of the system according to theinvention wherein determination units are provided for the flow ofcombustion air and for fuel consumption.

[0074]FIG. 13 is an embodiment which makes possible the conditioning ofthe intake air and the simulation of the ambient pressure, particularlyhigh-altitude simulation, and it makes the analysis of exhaust gaspossible as well.

[0075] The system according to the invention, having already anintegrated conditioning path (as seen in the direction of the air flow)consists of a dust filter 5 having an intake opening 4, a device formovement of air 6, preferably a radial fan or a blower, a butterflyvalve for negative pressure operation 7, and air cooler 8—preferably andair/cold-water heat exchanger having a throughput of a cooling mediumthat is adjustable for cold water 9—a mist collector for condensate 10,as well as an air heater 11 that is adjustable in its heating capacityby means of a control device 12. A vaporizer 13 can be arranged tocontrol humidity from which vapor can be metered into the main airpassage 15 via a vapor metering valve 14 to adjust the humidity. Anabsolute pressure sensor 16, a temperature sensor 17 and a humiditysensor 18 serve to measure the condition of the air.

[0076] The conditioned air in these system components is moved throughthe main air line 15 of the branching off point 19 between the main line20 and the intake passage 2 at a quantity that corresponds to themaximum quantity used by the engine. Thus, always the same quantity ofincoming air is to be treated by the conditioning path 4 through 18upstream, which makes the design extremely simple—particularly theconditioning. All changes in the operation of the engine to be testedcan thereby be included as well, even all highly dynamic transitionelements, and a constant conditioned quantity of combustion air issupplied at each instant to the internal combustion engine 1. A smallspeed-controllable axial fan 21 can be optionally arranged in the mainpassage 20 for compensation of pressure loss or for adjustment of aprecisely defined pressure differential between the intake passage 2 andthe exhaust gas passage of the engine 1, whereby said fan 21 is adjustedin its speed with the aid of the controlling device 33 depending on thedifferential pressure between the intake and discharge of line 20.Measuring of this differential pressure is conducted with thedifferential pressure sensor 22. The line 20 and the exhaust gas passage3 of the internal combustion engine 1 run via a merging piece 23 intothe air evacuation passage 24. A butterfly valve for positive pressureoperation 25 is arranged at the end of said air evacuation passage 24.An air-moving device 26 for negative pressure operation—preferably aradial fan or a blower—is disposed upstream from the air evacuationopening 27 for the discharge of the air-evacuation flow into theatmosphere or into the exhaust gas system of the test bench. Anadditional heat exchanger could possibly be arranged between theinternal combustion engine 1 and the air-moving device 26, preferably inthe air evacuation passage 24, whereby the design of the air-movingdevice is simplified and the choice of possible other types (of devices)is widened and problems are avoided through the exhaust gas/air mixturedownstream from the combustion engine 1 and/or through the operation atgreat negative pressure (up to 350 to 400 mbar.)

[0077] An electronic adjustment and control device 28 is provided forthe operation of the system and to set the desired air conditions intowhich devices there are integrated all necessary adjustment devicesrequired for the operation of the equipment and all control devices forpressure 29 and 30, temperature 31 and humidity 32. Consideration wasadvantageously given so that the mass flow is kept essentially constant,independent from the absolute pressure. For this purpose, one of thegas-moving devices 6, 26, 21 at the equipment-side is in controllingcommunication with the opposite control device 7, 25, relative to thecombustion engine 1, for the gas flow. Since there were heretofore onlysmall, insignificant pressure changes demanded in the positive pressureoperation, this control concept is mainly of importance for the negativepressure operation for which the control 7, which is arranged upstreamfrom the internal combustion engine 1, is in controlling communicationwith the gas-moving device 25 disposed downstream from the internalcombustion engine 1. The transporting capacity of the gas-moving device6, 26, 21, which most often depends on the (rotational) speed, is setaccording the position of the control device that is designed mostly asa throttle valve.

[0078] The functioning mode of the method can be described with the aidof FIG. 1 as follows:

[0079] The internal combustion engine 1 draws in the air mass flow ^(m&)_(in) required for combustion through the intake passage 2 and feedssaid air mass flow to the combustion. The developing exhaust gas massflow ^(m&) _(out) resulting from the combustion is subsequentlydischarged through the exhaust gas passage 3. It is the object of themethod to adjust the conditions of the air at the intake port of theintake passage 2, which means pressure, temperature and humidity,independent from ambient conditions. Moreover, the pressure at thedischarge port of the exhaust gas passage 3 should match the pressure atthe intake port of the intake passage 2 to a great extent. The air pathduring operation of the internal combustion engine on the test bench isthereby as follows: Based on the effect of the two air-moving devices 6,26, a defined air mass flow ^(m&) _(L) is moved through the intakeopening 4, through the air-moving device 6, the butterfly valve fornegative pressure operation 7, the air cooler 8, the mist collector 10,the air heater 11, and into the main air passage 15. At thebranching-off point 19 of the main passage 20 and the intake passage 2occurs a separation of the air mass flow ^(m&) _(L) into themain-passage air mass flow ^(m&) _(Bp) and into the exhaust-gas air massflow ^(m&) _(in). The bypass air mass flow ^(m&) _(Bp) is moved by aspeed-controllable axial fan for compensation of the pressure loss 21,and at the merging point 23 of the exhaust gas passage, said air massflow merges again into the main passage 20 together with the exhaust-gasmass flow ^(m&) _(out) onto the evacuation mass flow ^(m&) _(Ex). Saidevacuation mass flow ^(m&) _(Ex) is moved through the butterfly valvefor positive pressure operation 25, the air-moving device for negativepressure operation 26 and through the evacuation-air opening 27 into theatmosphere or into the evacuation-air system of the test bench.

[0080] The following relationships can be cited based on the law of massconservation and continuity as interrelationship of individual air massflows or exhaust-gas mass flows:

^(m&) _(in)=variable as function of the operational enginecondition.  (i)

^(m&) _(out)=^(m&) _(in)+^(m&) _(Br)  (ii)

[0081] whereby ^(m&)_(Br is the mass flow of the fuel required for combustion.)

[0082] However, the following is true for the use of conventional liquidof solid fuels or a nearly stoichiometric or super-stoichiometriccombustion method:

^(m&) _(Br)□^(m&) _(in)  (iii)

[0083] For example, in the use of commercial diesel fuel, thestoichiometric air requirement is 14.5 ^(kg air) _(/kg fuel) and true istherefore

[0084]^(m&) _(Br)=^(m&) _(in)/14.5, which validates the above mentioned(iii) interrelationship.

[0085] Based on (iii), a fuel mass flow can be neglected for a roughestimate of the mass flow and (ii) can also be stated as:

^(m&) _(out)≈^(m&) _(in)  (iv)

[0086] The air mass flows ^(m&) _(L) and ^(m&) _(Ex), which exist at thecomponents to control air conditions, and thereby the decisive valuesfor the quality of control of the method can be stated for alloperational conditions of the internal combustion engine (1) as follows:

^(m&) _(L)=^(m&) _(in)+^(M&) _(BP)  (v)

[0087] and

^(m&) _(Ex=) ^(m&) _(out)+^(m&) _(Bp)  (vi)

[0088] by using (iv) in (v) and (vi) it can thus be stated:

^(m&) _(L)≈^(m&) _(Ex)  (vii)

[0089] It is obvious thereby that the air mass flows ^(m&) _(L) and^(m&) _(Ex), which are decisive for the control of the condition of theair, are nearly independent from the operational condition of theinternal combustion engine 1 and its dynamic behavior are therefore onlydependent on the design and the operating mode of the technologicalcontrol component. It is thereby apparent that dynamic changes canfollow the operating mode of the internal combustion engine. A change inthe operating mode of the internal combustion engine causes merely achange of temperatures and thereby a change in the density of the airmass ^(m&) _(Ex). These changes may also be compensated with this methodthrough the behavior of the control device; however, these changes maybe influenced by the general design parameter of the system to a greatdegree, e.g. the size of the air mass flow flows ^(M&) _(L).

[0090] The control of the conditions of the air flow ^(m&) _(L) and thepressure of the air mass flow ^(m&) _(Ex) is performed as follows:

[0091] Control of Pressure at Positive Pressure Operation:

[0092] If the desired air pressure is to be higher than the ambientpressure, the control of the air pressure is performed through pressureincrease and movement of the air mass flow flow ^(m&) _(L) by theair-moving device 6 in cooperation with the butterfly valves forpositive pressure operation 25. The air-moving device 6 is operated atconstant speed whereby the air mass flow is chosen to be at least equal,advantageously even considerably greater, than the maximum airconsumption of the internal combustion engine 1. The pressure in theentire line system is raised to the desired air pressure throughthrottling of the air mass flow with the butterfly valve for positivepressure operation 25 from the discharge port at the air-moving device 6to the butterfly valve for positive operation. The position of thebutterfly valve for positive pressure operation 26 is adjusted therebyvia the electronic control device for the positive-pressure butterflyvalve 30. The actual pressure in the pipe system is thereby measured bythe absolute pressure sensor 16 and it is converted into an electricsignal proportional to the pressure. This signal is transmitted to thecontrol device for the positive-pressure butterfly valve 30 as actualsignal. The control device 30 compares the actual signal with thereference variable desired by the user and produces a reference signalfor the positive-pressure butterfly valve 26 whereby said referencesignal is proportional to the position of the butterfly valve. In thisoperating mode, the position of the negative-pressure butterfly valve 7is completely opened to avoid undesired throttle effects at this valve.

[0093] Control of Pressure at Negative Pressure Operation:

[0094] If the desired air pressure is to be lower than the ambientpressure, control of the air pressure is performed through throttling atthe butterfly valve for negative pressure operation 7 and throughmovement of the air mass flow ^(m&) _(L) by suction via the air-movingdevice for negative pressure operation 26. The air-moving device 26 isoperated at constant speed whereby the air mass flow is again chosen tobe at least equal to the maximum air consumption of the engine 1, againpreferably even considerably greater. Through throttling of the air massflow with the butterfly valve for negative air pressure 7, the pressurein the entire line system is lowered to the desired air pressure fromthe butterfly valve for negative pressure operation to the suction-sideof the air-moving device 26. The position of the butterfly valve fornegative pressure operation 7 is thereby adjusted by the electroniccontrol device for the negative-pressure butterfly valve 29. The actualpressure in the pipe system is thereby measured by the absolute pressuresensor 16 and it is converted to an electric signal proportional to thepressure. This signal is transmitted to the control device for thenegative-pressure butterfly valve 29 as actual signal. The controldevice 29 compares the actual signal with the reference variable desiredby the user and produces a reference signal for the negative-pressurebutterfly valve 7 whereby said reference signal is proportional to theposition of the butterfly valve. In this operating mode, the position ofthe butterfly valve for positive pressure 25 is completely opened toavoid undesired throttle effects at this valve.

[0095] Control of Temperature:

[0096] The adjustment of temperature of the air mass flow ^(m&) _(in)occurs with the aid of the effect of the air cooler 8 and the air heater11. Heating or cooling of the air mass flow can occur according to thedesired nominal temperature. The actual temperature is measured by thetemperature sensor 17 and is converted to an electric signalproportional to the temperature. This signal is transmitted to thecontrol device for temperature 31 as actual signal. The control device31 compares the actual signal with the reference variable desired by theuser and it produces a steady reference signal to the control valve forcold water 9 or to the regulating device for the output of heat 12.Adjustment of the desired nominal temperature is performed therebythrough adjustment of the required cycling of a cooling medium throughthe air cooler and/or adjustment of the required heat output of the airheater. Operational conditions could develop that require cooling andsubsequently heating as well (see also control of humidity.)

[0097] Control of Humidity in Air:

[0098] Adjustment of humidity of the air mass flow ^(m&) _(in) occurswith the aid of the effect of the air cooler 8 and through metering ofvapor from the vapor generator 13. The air mass flow ^(m&) _(L) iscooled down in the air cooler to below the dew point and is dried as aresult of the thereby caused condensation of the humidity contained inthe air flow. The developing condensate is collected during the flowthrough the mist collector and is (subsequently) discharged. Theadjustment of the desired humidity occurs through metering of watervapor into the air flow of the main air passage 15. The actual humidityis measured by the humidity sensor 18 and is converted to an electricsignal proportional to the humidity. This signal is transmitted to thecontrol device for humidity 32 as actual signal. The control device 32compares the actual signal with the reference variable desired by theuser and produces a steady reference signal for the control valve forcold water 9 or for the vapor metering valve 14 depending on therequirement for cooling (dehumidifying) or humidifying.

[0099] With the two above-mentioned control values is also the goalconnected to prevent condensation (of mainly water vapor) in the dilutedexhaust gas. The temperature of the diluted exhaust gas must thus behigher than its dew point, which is generally lower than 52° C. for theundiluted exhaust gas. Therefore, a heating device can be providedadditionally for the combustion gas flowing through the main air passage15. However, the exhaust gas of the internal combustion engine is mostoften much hotter than the gas used to dilute the exhaust gas (namelythe combustion gas not required by the internal combustion engine 1) sothat the diluted exhaust gas is heated up relative to the diluent gasand no condensation develops in (almost) all cases—even withoutadditional heating.

[0100] Compensation for Pressure Loss in the Main Line:

[0101] A speed-controllable axial fan 22 can be arranged in the line 20if it is necessary based on special requirements in the quality ofpressure control of the air mass flow in the exhaust gas passage.Pressure loss in line 20 is measured by the differential pressure sensor22 and transmitted as an electric actual signal to the speed-controldevice for the axial fan 21. This setting of speed occurs in such amanner that pressure loss is compensated in the main line 20 asillustrated in FIG. 2.

[0102] If the control accuracy of the exhaust gas backpressure controlallows, and there is allowed a small pressure differential to be setprecisely between the intake passage 2 and the exhaust gas passage 3,one can do away with speed-controllable axial fan for pressure losscompensation 21 (see FIG. 1) as well as the control device for the axialfan 33.

[0103] Embodiment Variation for Pure Positive Pressure Operation:

[0104]FIG. 3 shows an embodiment variation that is suitable for purepositive pressure operation (relative to the ambiance.) In comparison toFIG. 1, this embodiment is illustrated by leaving off the components togenerate the negative pressure. In this embodiment are missing therebythe butterfly valve for negative pressure operation 6 of FIG. 1, theair-moving device for negative pressure operation 26, as well as thecontrol device for the negative-pressure butterfly valve 29.

[0105] Embodiment Variation for Pure Negative Pressure Operation (FIG.4):

[0106]FIG. 4 shows an embodiment variation that is suitable for purenegative pressure operation (relative to the ambiance.) In comparison toFIG. 1, this embodiment is illustrated by leaving off the components togenerate the positive pressure. In this embodiment are missing therebythe butterfly valve for positive pressure operation 6, the butterflyvalve for positive pressure operation 25, as well as the control devicefor the positive-pressure butterfly valve 30 of FIG. 1

[0107] Embodiment Variation for Highly Precise Air Pressure Control(FIG. 5):

[0108]FIG. 5 shows an embodiment of the invention wherein highly preciseair pressure control can be realized, that is, for positive pressure aswell as for negative pressure. The butterfly valves 6, 25 used forsetting the positive pressure or the negative pressure are supplementedthrough the parallel employment of a respective precision-control valve7 a, 25 a, which is dimensioned clearly smaller in flow cross sectionthat the butterfly valves. In this case, setting of the desired airpressure occurs in such a manner that rough adjustment of the airpressure is performed in the beginning with the butterfly valve 7 or 25.After falling below a defined control deviation relative to the actualpressure from the reference pressure, the position of these butterflyvalves 7, 25 is maintained and is not changed any more thereafter. Thefinal setting of the desired air pressure occurs subsequently thereofwith the aid of the precision-control valve 71 and 25 a.

[0109] This embodiment variation has the advantage that, on one hand,the air pressure can be brought very quickly near the desired value withthe aid of the butterfly valves 7, 25—and, on the other hand, highlyprecise pressure control can be realized with the finely-tunedprecision-control valves 7 a, 25 a.

[0110] In practice, it is especially advantageous if the conditions onthe test bench correspond exactly to the conditions existing in thedetermining operation of the test piece, particularly in vehicleengines, which means also the conditions of air filters, exhaust gassystem etc. provided on the vehicle. As schematically illustrated inFIG. 6, the supply line is therefore designed in such a manner that thelength of the supply line 15 for the conditioned combustion air, betweenthe branching-off point 19 of the intake passage 2 to the internalcombustion engine 1 and the merging point 23 of the exhaust gas line 3is as long as the complete engine unit, including all components of theintake section upstream and the components of the exhaust sectiondownstream (of the engine), which means that the length between thebranching-off point 19 and the merging point 23 corresponds to thedistance between the air filter intake 1 a and the end of the mufflersystem 1 b of the vehicle.

[0111]FIG. 7 shows an additional advantageous embodiment of the systemthat corresponds in its basic design to the one in FIG. 6, except thatthe entire engine, including air filter 1 a, muffler system 1 b, intakepassage 2, and exhaust gas passage 3 are disposed in an closeable andsealable box 28 relative to the ambiance, and whose inner pressure isbrought to the pressure of the line 15 through line 29. FIG. 8 showsthat the box in FIG. 7 can be designed as a through-flowing section 28 aof line 15. It is possible thereby that the engine draws its intake airdirectly from this box so that the branching-off point 19 becomeslocated at the intake point of the engine 1, which means through theopen end of the intake passage 2. This of advantage since a pipe doesnot have to be connected to the intake point of the engine, whichnegatively influences the behavior of the intake section 1 a, 2 in somecases.

[0112] In the following is to be described the development of theinventive method or the device according to the invention relative tothe exhaust gas testing technology whereby the existing quantities ofpollutants in the exhaust gas of the engine are to be determined fromthe measured values of the pollutant concentrations. This isadvantageously achieved in the present case by means of a so-called CVS(constant volume sampling) system, which is standardized and which hasestablished precise devices for the determination of the quantities ofpollutants in the exhaust gas. The specified high dilution factors canbe reached by diverting the exhaust gas of the internal combustionengine 1 into the combustion gas not required for the combustion processand which bypasses said engine. There is also made possible theprecisely defined dilution of the exhaust gas with the conditioning ofthese combustion gases—and now also of the diluent gas at the sametime—through the advantageously possible combination and made possibleis thereby a precise determination of the quantities of pollutants in asimple and reliable manner.

[0113] For determination of the quantities of exhaust gas pollutants inthe measurable pollutant concentrations there can be measured thequantity of exhaust gas that either flows directly at the point ofsampling—or there will be used the mass balance equation (masscombustion air+fuel mass=exhaust gas mass), which has to be inevitablytrue for the inventive system consisting of the engine and theaccompanying supply and discharge passages for the combustion air or theexhaust gas. It is thereby especially advantageous if the mass flow ofthe discharging exhaust gas is kept constant. This can be achievedthrough known means such as a critical nozzle or a Roots blower.

[0114] The combustion air bypassing the internal combustion engine 1,which is subsequently used for dilution of the exhaust gas, should be amultiple of the maximum quantity of intake air of the engine so that theexhaust gas is diluted by the same quantity (or more) of diluent air. Agenerally known CVS system could also be retrofitted in an especiallyadvantageous manner and used for conditioning of the intake airaccording to the invention whereby the intake air of the motor is takenfrom the conditioned fresh air of the CVS system and the exhaust gas isfed to the exhaust gas diluting system as proposed in the CVS system.

[0115] The inventive system is advantageously employed to condition theintake air to overcome the difficulties in measuring of the intake-airmass flow or exhaust-gas mass flow for analysis of the more or lessdiluted exhaust gas and said system is used for relatively minordilution whereby the necessary flow measurement in the region of thesupplied, conditioned intake air occurs still upstream from thebranching-off point of the bypass line. This has the advantage thathighly precise sensors can be employed for a nearly constanct andpulsation-free air flow even at dynamic operation of the engine.

[0116] For additional improvement in measuring the intake-air mass flowor the exhaust-gas mass flow for analysis of the more or less dilutedexhaust gas, it is proposed that the inventive system is employed tocondition the intake air and used for exhaust gas analysis withcomparatively minor dilution.

[0117] It may be furthermore proposed that in exhaust gas analysis, anadditional dilution system is used for employment after the relativeminor exhaust gas dilution by the inventive system, which allows apossibly required additional exhaust gas dilution. This can be ofadvantage especially when the necessary conditioning requirements differto a great degree from the operation of the engine and from theimportant dilution of exhaust gas.

[0118] A first embodiment example for a system to measure the quantitiesof pollutants is illustrated in FIG. 9 whereby said system correspondsto the one in FIG. 6 in its basic design, except that there is providedin line 24 a measuring point 30 for an exhaust gas analyzer 31 as wellas a measuring point 32 for a flow determination device 33. Thedetermination of flow is performed in line 24 with an exhaust-gas massflow sensor, but in many cases determination will be sufficient usingexhaust gas pressure sensors and temperature sensors under considerationof an calibration factor and possibly additional signals of the unit 25,26 (e.g. the speed of a Roots blower), which signals can be transmittedvia the signal line 34 illustrated by a dotted line.

[0119] In some cases, for example during measuring of particle contentand hydro carbon content in the exhaust gas of diesel fuel, thetemperature of the diluent air at point 23 must not drop below a certainlimit, for instance 50° C., since otherwise exhaust gas constituents maycondense and break down. It would therefore be necessary to provide aheating element (nor illustrated) in line 15 between points 19 and 23that subsequently heats up the conditioned air in the conditioningsystem 5-18 to the required diluting temperature. It could be possiblyalso be necessary for the protection of the intake fan to cool theexhaust gas for exhaust gas analysis downstream from the measuringpoint. An additional measuring point 35 may advantageously be providedfor the determination of the pollutant concentration of the diluent gasin the supply passage 15, upstream of its merging point 23 into theexhaust gas passage, preferably even upstream of the branching-off point19 of the intake passage 2 leading to the internal combustion engine 1.A line 36 leads from this measuring point 35 to the exhaust gas analyzer31.

[0120]FIG. 10 corresponds to FIG. 9, except that one determinationdevice 37 is assigned not for the flow of diluted exhaust gas in 24 butfor the entire quantity of air upstream from point 19. the unit 37 ispreferably again a gas-mass flow sensor; however, in many casesdetermination will be sufficient using gas pressure sensors andtemperature sensors under consideration of a calibration factor andpossibly additional signals of the unit 5-18 (for instance, the speed ofa Roots blower), whereby said signals can be transmitted by the signalline 38 illustrated by a dotted line. However, there is need heresupplementary a determination unit 39 for fuel consumption with ameasuring point 40 on the engine 1 or in the fuel delivery system of theengine.

[0121]FIG. 11 corresponds to FIG. 6, except that the measuring point 30for an exhaust gas analyzer 31 is arranged in the exhaust gas line 3 andserves also for analysis of the undiluted exhaust gas. For conversion ofthe pollutant concentration to pollutant quantities is could be possiblydesirable to provide a measuring point 41 for a determination unit 42 todetermine the flow of the undiluted exhaust gas in line 3.

[0122]FIG. 12 corresponds to FIG. 11, except that determination units 42are herein provided for the intake air of the engine with a measuringpoint 43 in line 2 and for fuel consumption 39, 40 (similar to FIG. 10.)

[0123]FIG. 13 could be a preferred embodiment that makes possible, in anespecially advantageous manner, the conditioning of intake air andambient pressure simulation, particularly high-altitude simulation, aswll as exhaust gas analysis. It is shown that element 19 is designedhaving an enlarged, flow-through volume as part of line 15, which makespossible thereby free intake of the conditioned air through the intakesystem 2 and 1 a of the engine. This volume 19 is disposed within thebox 28 together with the intake system 1 and the engine 1 as well as theexhaust gas system 1 b whereby said box 28 is still in pressurizedcommunication with line 15 via line 29. This has the advantage that theexhaust gas analysis is not disrupted by possible vapors from the dirton the outside of the engine. Even so, it cannot be completely ruled outthat pollutants from said box enter the passage 15 through the pressureconnection line 29, even though box 28 has no cross flow of diluent airin this case. It can thereby be of advantage if, in contrast to FIG. 9,the measuring point 35 for possible existing pollutants of the diluentair are arranged in the passage 15 only downstream from the connectionpoint of line 29, for example, but still upstream of point 23, ofcourse. The measuring points 30 and 32 for flow and pollutantconcentration of the diluted exhaust gas are provided on line 24, justas in FIG. 9.

1. A method for supplying an internal combustion engine with conditionedgas, particularly air, preferably on test benches, including the supplyof humidity and/or temperature-conditioned gas to the internalcombustion engine, characterized in that an essentially constant andfully conditioned quantity of combustion gas is provided at each instantwhereby said quantity corresponds to at least the maximum quantityrequired by the respective internal combustion engine.
 2. A methodaccording to claim 1, whereby the combustion gas not used by theinternal combustion engine bypasses the internal combustion engine andis then mixed with its exhaust gas.
 3. A method according to claim 1 or2, whereby the combustion air/exhaust gas mixture downstream from theengine is suctioned out, preferably with a defined negative pressurerelative to the atmospheric pressure.
 4. A method according to one ofthe claims 1, 2 or 3, whereby the combustion gas is delivered to theinternal combustion engine under increased pressure relative to theatmospheric pressure—or unneeded combustion gas is diverted to bypassthe internal combustion engine.
 5. A method according to one of theclaims 1 through 4, whereby between the conditioned combustion gas andthe exhaust gas or the combustion gas/exhaust gas mixture there is set apressure drop, downstream from the internal combustion engine, between0.3 and 5 mbar, preferably between 0.5 and 3 mbar.
 6. A method accordingto one of the claims 1 through 5, whereby the flow is kept essentiallyconstant, independent from the absolute pressure.
 7. A method accordingto one of the claims 1 through 6, whereby the direct ambiance of theinternal combustion engine is kept at the same pressure as the pressureof the conditioned combustion gas.
 8. A method according to claim 7,whereby the internal combustion engine is surrounded by a flow ofconditioned combustion gas.
 9. A method for determining the quantitiesof pollutants in the exhaust gases of an internal combustion engine,including the determination of the pollutant concentration and thequantity of the flowing exhaust gas whereby diluting of the exhaust gastakes place by using a diluent gas of known composition, characterizedin that an essentially constant and fully conditioned quantity ofhumidity and/or temperature-conditioned combustion gas is supplied tothe internal combustion engine at each instant whose quantitycorresponds to at least the maximum quantity required by the respectivecombustion engine, and whereby the exhaust gas is diluted with thequantity of combustion gas that is not used by the internal combustionengine.
 10. A method according to claim 9, whereby the flow of exhaustgas, diluted by the quantity of unused combustion gas, is kept constantand whereby there is determined the quantity of combustion gas suppliedto the internal combustion engine as well as the quantity of fuel.
 11. Amethod according to claim 9, whereby the flow of discharging exhaustgas, diluted by the unused quantity of combustion gas, is kept constantand is defined.
 12. A method according to claim 9, whereby the flow ofthe supplied combustion gas is kept constant, and its quantity and thequantity of fuel supplied to the internal combustion engine isdetermined.
 13. A method according to claim 9, whereby the flow of thesupplied combustion gas is kept constant and the flow of the dilutedexhaust gas is determined.
 14. A method according to one of the claims10 through 13, whereby the determination of pollutant concentrationoccurs in the exhaust gas, which is diluted with the quantity ofcombustion gas not used by the internal combustion engine.
 15. A methodaccording to one of the claims 10 through 13, whereby the determinationof pollutant concentration occurs in the undiluted exhaust gas.
 16. Amethod according to one of the claims 10 through 15, whereby thepollutant concentration in the available combustion gas is determined inaddition.
 17. A method according to one of the claims 9 through 16,whereby the quantity of available combustion gas is a multiple of themaximum quantity required by the combustion engine.
 18. A methodaccording to one of the claims 9 through 17, whereby the combustiongas/exhaust gas mixture downstream from the internal combustion engineis moved by suction, preferably by a defined negative pressure relativeto the atmospheric pressure.
 19. A method according to one of the claims9 through 17, whereby the combustion gas is delivered to the internalcombustion engine through increased pressure relative to the atmosphericpressure or whereby unneeded combustion gas bypasses the internalcombustion engine.
 20. A method according to one of the claims 9 through19, whereby a pressure drop is set between 0.3 and 5 mbar, preferablybetween 0.5 and 3 mbar, between the conditioned combustion gas and theexhaust gas or between the combustion gas/exhaust gas mixture downstreamfrom the internal combustion engine.
 21. A method according to one ofthe claims 9 through 20, whereby the flow is kept essentially constant,independent from the absolute pressure.
 22. A method according to one ofthe claims 9 through 21, whereby the direct ambiance of the internalcombustion engine is kept at the same pressure as the pressure of theconditioned combustion gas.
 23. A method according to claim 22, wherebya flow of conditioned combustion gas surrounds the internal combustionengine.
 24. A device to supply an internal combustion engine withconditioned combustion gas, particularly air, preferably on testbenches, comprising a supply line leading to the internal combustionengine for humidity and/or temperature-conditioned combustion gas,characterized in that the supply line or supply passage (15) is designedfor the maximum quantity of combustion gas required by the respectiveinternal combustion engine (1), and whereby a intake line (suction pipe)2, which can be connected to said internal combustion engine (1),branches off from said supply line (15).
 25. A device according to claim24, wherein an exhaust gas line (3), connectable to the internalcombustion engine (1), joins the supply line (15) downstream from thebranching-off point of the intake line(2).
 26. A device according toclaim 24 or 25, wherein there are provided elements (e.g. 21) for theadjustment of a pressure differential in the range between 3.5 and 5mbar, preferably between 0.5 and 3 mbar, which are disposed between thebranching-off point of the intake line (2) and the merging point of theexhaust gas line (3) with the respective supply line (15).
 27. A deviceaccording to one of the claims 24 through 26, wherein there are provideddevices (e.g. 21) to ensure a minimum flow rate between thebranching-off point of the intake line (2) and the merging point of theexhaust gas line (3), at least corresponding to the diffusion rate ofexhaust gas in the conditioned combustion gas.
 28. A device according toone of the claims 24 through 27, wherein the devices (8-18) foradjustment and control of the temperature and/or humidity are providedupstream from the branching-off point of the intake line (2) in thesupply line (15) leading to the internal combustion engine (1), e.g. gascoolers, mist eliminators, gas heaters and vapor delivery lines,preferably having vapor metering valves.
 29. A device according to oneof the claims 24 through 28, wherein a gas-moving device (6) is disposedupstream from the branching-off point of the intake line (2) and acontrol device (25, 25 a) is provided downstream from the merging pointof the exhaust gas line (3) for the gas flow.
 30. A device according toone of the claims 24 through
 29. wherein a control device (7) for thegas flow is provided upstream from the branching-off point of the intakeline (2) and a gas-moving device (26) is provided downstream from themerging point of the exhaust gas line (3).
 31. A device according toclaim 30, wherein at least one heat exchanger is provided between theinternal combustion engine (1) and the gas-moving device (26).
 32. Adevice according to claim 29, 30 or 31, wherein the control devices (7,25) for the gas flow are in the form of butterfly valves.
 33. A deviceaccording to claim 32, wherein at least one precision control valve (25a) is provided parallel to the butterfly valves (7, 25).
 34. A deviceaccording to one of the claims 24 through 33, wherein a gas-movingdevice (21) is provided between the branching-off point of the intakeline (2) and the merging point of the exhaust gas line (3).
 35. A deviceaccording to one of the claims 24 through 34, wherein devices areprovided for the laminarization of the flow in the supply line,preferably at least between the branching-off point of the intake line(2) and the merging point of the exhaust gas line (3).
 36. A deviceaccording to one of the claims 24 through 35, wherein a shock dragand/or a muffler is/are provided in the supply line (15) between thebranching-off point of the intake line (2) and the merging point of theexhaust gas line (3).
 37. A device according to one of the claims 24through 36, wherein at least one of the gas-moving devices 6, 26, 21) isin controlled communication with the opposite control device (7, 25),relative to the internal combustion engine (1), for the gas flow.
 38. Adevice according to claim 37, wherein the moving capacity of thegas-moving device (6, 26, 21) is adjustable dependent on the position ofthe control device (7, 25) disposed on the opposite side.
 39. A deviceaccording to one of the claims 24 through 38, wherein the distancebetween the branching-off point (19) of the intake line (2) and themerging point (23) of the exhaust gas line (23) correspondssubstantially to the distance between the air filter intake (1 a) andthe end of the muffler system (1 b) of the vehicle whose internalcombustion engine (1) is supplied with conditioned combustion gas.
 40. Adevice according to one of the claims 24 through 39, wherein a closedspace (28) is provided to receive the internal combustion engine (1) andwhereby said closed space (28) is connected to the section of the supplyline (15) between the branching-off point of the intake line (2) and themerging point of the exhaust gas line (3).
 41. A device according to oneof the claims 24 through 39, wherein a closed space (28 a) is providedto receive the internal combustion engine (1) in the section between thebranching-off point of the intake line (2) and the merging point of theexhaust gas line (3).
 42. A device to determine the quantities ofpollutants in the exhaust gas of an internal combustion enginecomprising at least one measuring point, for example a sensor orsampling device, for determination of the pollutant concentration, and adetermination device for the flow of gas whereby said determinationdevice is provided with a passage leading from the exhaust gas passageto the supply passage for a diluent gas of known composition,characterized in that the supply passage (15) for the diluent gas isdesigned for at least the maximum quantity of combustion gas required bythe respective internal combustion engine (1) and whereby an intake line(2), which can be connected to the internal combustion engine (1),branches off from said supply passage (15).
 43. A device according toclaim 42, wherein the supply passage (15) for the diluent gas isdesigned for a multiple of the maximum quantity of combustion gasrequired by the respective internal combustion engine (1).
 44. A deviceaccording to claim 42 or 43, wherein the measuring point (30) todetermine the pollutant concentration is arranged in the exhaust gaspassage (24), downstream from the merging point (23) of the exhaust gaspassage (3) into the supply passage (15) for the diluent gas.
 45. Adevice according to claim 42 or 43, wherein the measuring point (30) forthe determination of the pollutant concentration in the exhaust gaspassage (3) is arranged upstream from its merging point into the supplypassage (15) of the diluent gas.
 46. A device according to one of theclaims 42 through 45, wherein an additional measuring point (35) todetermine the pollutant concentration in the supply passage (15) for thediluent gas is provided upstream from the merging point of the exhaustgas passage (3) into said supply passage (15).
 47. A device according toone of the claims 44 through 46, wherein the determination device (32,33; 41, 42) for the flow of gas is arranged in the same section as themeasuring point (30) for the determination of the pollutantconcentration.
 48. A device according to one of the claims 44 through46, wherein the determination device (37, 38; 38 a) for the flow of gasif provided in the supply line (15) for the diluent gas.
 49. A deviceaccording to one of the claims 44 through 48, wherein a measuring device(39, 40) is provided for the fuel mass delivered to the internalcombustion engine (1).